(a) Field of the Invention
The present invention relates to an apparatus for manufacturing compacted irons and an apparatus for manufacturing molten irons provided with the same, more specifically to an apparatus for manufacturing compacted irons of reduced materials containing direct reduced irons and an apparatus for manufacturing molten irons provided with the same.
(b) Description of the Related Art
The iron and steel industry is a core industry that supplies the basic materials needed in construction and in the manufacture of automobiles, ships, home appliances, etc. Further, it is one of the oldest industries which have advanced since the dawn of human history. Iron works, which play a pivotal role in the iron and steel industry, produce steel from molten iron, and then supply it to customers, after producing molten irons (i.e., pig irons in a molten state) using iron ores and coals as raw materials.
Currently, approximately 60% of the world's iron production is produced using a blast furnace method that has been in development since the 14th century. According to the blast furnace method, iron ores, which have gone through a sintering process, and cokes, which are produced using bituminous coals as raw materials, are charged into a blast furnace together and oxygen is supplied thereto to reduce the iron ores to irons, and thereby manufacturing molten irons. The blast furnace method, which is the most popular in plants for manufacturing molten irons, requires that raw materials have a strength of at least a predetermined level and have grain sizes that can ensure permeability in the furnace, taking into account reaction characteristics. For that reason, cokes that are obtained by processing specific raw coals are needed as carbon sources to be used as a fuel and as a reducing agent. Also, sintered ores that have gone through a successive agglomerating process are needed as iron sources. Accordingly, the modern blast furnace method requires raw material preliminary processing equipment, such as coke manufacturing equipment and sintering equipment. Namely, it is necessary to be equipped with subsidiary facilities in addition to the blast furnace, and to also have equipment for preventing and minimizing pollution generated by the subsidiary facilities. Therefore, a heavy investment in the additional facilities and equipment leads to increased manufacturing costs.
In order to solve these problems with the blast furnace method, significant effort has been made in iron works all over the world to develop a smelting reduction process that produces molten irons by directly using raw coals as a fuel and a reducing agent and by directly using fine ores, which account for more than 80% of the world's ore production.
An installation for manufacturing molten irons directly using raw coals and fine iron ores is disclosed in U.S. Pat. No. 5,534,046. The apparatus for manufacturing molten irons disclosed in U.S. Pat. No. 5,534,046 includes three-stage fluidized-bed reactors forming a bubbling fluidized bed therein and a melter-gasifier connected thereto. The fine iron ores and additives at room temperature are charged into the first fluidized-bed reactor and successively go through three-stage fluidized-bed reactors. Since hot reducing gas produced from the melter-gasifier is supplied to the three-stage fluidized-bed reactors, the temperature of the iron ores and additives, which were at room temperature, is raised by contact with the hot reducing gas. Simultaneously, 90% or more of the iron ores and additives are reduced and 30% or more of them are sintered, and they are charged into the melter-gasifier.
A coal packed bed is formed in the melter-gasifier by supplying coals thereto. Therefore, iron ores and additives at room temperature are melted and slagged in the coal packed bed and are then discharged as molten irons and slags. The oxygen supplied from a plurality of tuyeres installed on the outer wall of the melter-gasifier burns a coal packed bed and is converted to a hot reducing gas. Then, the hot reducing gas is supplied to the fluidized-bed reactors, and thereby reducing iron ores and additives and is exhausted outside.
However, since a high-speed gas flow is formed in the upper portion of the melter-gasifier included in the above-mentioned apparatus for manufacturing molten irons, there is a problem in that the fine reduced irons and sintered additives charged into the melter-gasifier are scattered and loosened. Furthermore, when fine reduced irons and sintered additives are charged into the melter-gasifier, there is a problem in that permeability of gas and liquid in the coal packed bed of the melter-gasifier cannot be ensured.
For solving these problems, the method for briquetting fine reduced irons and additives and charging them into the melter-gasifier has been developed. Relating to the above development, U.S. Pat. No. 5,666,638 discloses a method for manufacturing oval-shaped briquettes made of sponge irons and an apparatus using the same. In addition, U.S. Pat. Nos. 4,093,455, 4,076,520 and 4,033,559 disclose a method for manufacturing plate-shaped or corrugated briquettes made of sponge irons and an apparatus using the same. Here, fine reduced irons are hot briquetted and then cooled, and thereby they are manufactured into briquettes made of sponge irons in order to suitably transport them a long distance.
When the briquettes made of sponge irons are manufactured by using the above-mentioned method, a plurality of problems occur. This will be explained in detail below.
First, hot briquettes manufactured by using the above-mentioned method can be temporarily stored or be charged into the melter-gasifier and melted therein. In this case, hot briquettes are transported to a temporary storage bin or a melter-gasifier through a transporting chute. Since the temperature of hot briquettes is about 700° C., the transporting chute is impacted by the briquettes. Therefore, the transporting chute is thermally expanded and is thermally contracted, and thereby it is seriously worn or deformed. In this case, the transporting chute is blocked since it is distorted or broken. In particular, when hot briquettes are crushed and transported, there is a great possibility that the transporting chute will be blocked since fine reduce irons are generated.
For solving these problems, a transporting chute made of a stainless steel having thermal resistance and wear resistance has been used. Since the transporting chute made of a stainless steel has a high thermal expansion ratio, the transporting chute is multiply-divided and a separating space is formed therebetween for thermal expansion.
However, continuous problems occur in which the transporting chute is not only blocked since hot briquettes are accumulated in the separating space between the transporting chutes, but also that is breaks due to thermal deformation. In addition, a few parts of the transporting chute, which are broken, then enter a following apparatus which then becomes out of order. Furthermore, it is difficult to maintain the transporting chute due to hot reduced irons accumulated in the transporting chute.
Second, the briquettes manufactured by using the above-mentioned method are not suitable to be melted in the melter-gasifier. Generally, the density of briquettes, which are suitable to be melted in the melter-gasifier, is preferably in a range of 3.5 ton/m3 to 4.2 ton/m3. However, the briquettes made of sponge irons by using the above-mentioned method are not suitable for use in the melter-gasifier since the density thereof is too high. In addition, when the briquettes made of sponge irons are directly used in the melter-gasifier, it is not necessary for them to have a shape or strength sufficient to transport them a long distance. Therefore, when the briquettes made of sponge irons, which are manufactured by using the above-mentioned method, are charged into the melter-gasifier and then molten irons are manufactured, the cost for manufacturing molten irons is raised due to a greater use of energy than is necessary.
In addition, when briquettes made of sponge irons, whose grain size is not controlled, are charged into the melter-gasifier, briquettes made of sponge irons, which are not melted, fall to the front end of a tuyere for injecting oxygen, and thereby the tuyere for injecting oxygen is blocked. Therefore, a burning flame, which is formed from the front end of the tuyere for injecting oxygen into the coal packed bed, is backfired to the tuyere for injecting oxygen, and thereby damaging the tuyere resulting in poor operation of the melter-gasifier.
Third, it is difficult to smoothly transport the briquettes made of sponge irons when the briquettes are crushed by the crusher. In this case, a guide chute is used in order to suitably guide the compressively molded reduced irons to the crusher. However, the compressively molded briquettes are not successively discharged and are not smoothly charged into the crusher. Then, the middle portions thereof are broken, generating fine particles. Furthermore, there is a problem that a thermal load of the crusher, which follows the guide chute, is increased.